The present invention relates to a method for forming a bevel cut at an end of a wood member.
Wood members including wood boards such as plywood, veneer laminated lumber (LVL), fiber board and also sheets such as veneer are joined together in an end-to-end manner in various joints using thermosetting or thermoplastic adhesive for producing a wood member with an increased length. For achieving the desired joint strength, the ends of a wood member are bevel cut so as to enlarge the area of the cut end surfaces to be coated with adhesive. Wood members are assembled with the opposing bevel cut ends coated with adhesive and lapped one on the other and the joining of the wood members is accomplished by allowing the adhesive to be set by heating or cooling depending on the type of the adhesive used.
For increasing the joint strength by further expanding the joint surface area, a wood member is formed at an end thereof with a series of groove-like V-shaped bevel cuts each extending from one surface to the other surface of the wood member and having two contiguous surfaces inclined so as to form a V-shape at any section across the bevel cuts, as shown in FIG. 24. As seen from the drawing, any two inclines surfaces of any two different adjacent groove-like bevel cuts form a ridge-like projections and two wood members are joined together with ridge projections fitted in the groove-like bevel cuts. The bevel cuts are formed in such a position that two wood members joined together at the two opposing ends thereof form a rectangular shape.
A method for forming such V-shaped bevel cuts will be explained in the following with reference to FIGS. 22 through 25.
FIG. 22 shows an example of a cutter assembly 11 having a plurality of cutters 3 mounted on a common rotatable shaft 2. Each cutter 3 has a plurality of cutting edges 3A arranged in the circumferential direction and any two adjacent cutting edges 3A in the circumferential direction of each cutter 3 are inclined in opposite direction with respect to an imaginary line extending parallel to the axis of the shaft 2 on which the cutters 3 are mounted. The cutters 3 are mounted on the shaft 2 in side-to-side contact with each other and disposed on the shaft 2 so that the cutting edges 3A of the respective cutters 3 are staggered in the circumferential direction as indicated by dashed-dotted spiral curved lines in FIG. 22 for the purpose of reducing the load acting on the cutter assembly 11 during cutting to form the bevel cuts.
FIG. 23 shows the movement of the cutter assembly 11 installed in a bevel cut forming apparatus with respect to a wood board 210 as a wood member to be cut. The cutters 3 rotating at a high speed in arrow direction are movable reciprocally along a path that is indicated by double-headed arrow between the raised standby position indicated by solid line and the lowered position indicated by dotted line. The path along which the cutter assembly 11 moves reciprocally is inclined at an angle (θ), for example, of about 10°.
As shown in FIG. 23, the wood board 210 is moved forward by a plurality of feeding rolls 220 (only one roll being shown in the drawing) to a position on a support table 215. Then, the rotating cutter assembly 11 is moved downward along the inclined path to its lowered position. As a result, a series of groove-like V-shaped bevel cuts 210A is formed at the leading end of the wood board 210 at an angle of θ with respect to the opposite surfaces of the wood board 210, as shown in FIG. 24. Before the cutting is made, the wood board 210 is stopped at a such a position on the support table 215 that each resulting bevel cut 210A extends between the opposite top and bottom surfaces of the wood board 210.
The support table 215 on which the wood board 210 is supported is made of a material such as synthetic resin that is rigid and hard only to such an extent that the cutting edge 3A of a rotating cutter 3 is not broken by contact with the support table 215. Furthermore, as clearly shown from FIG. 23, the leading end of the support table 215 with respect to the wood board feeding direction indicated by arrow is formed with a cutout 215A that allows the cutting edges 3A of the rotating cutters 3 to move past support table 215 without mechanically interfering with the support table 215.
The cutout 215A of the support table 215 may be formed by firstly fixing a wood board such as 210 on the support table 215 and moving the rotating cutter assembly 11 downward along an inclined path that is located above and parallel to the aforementioned inclined path shown in FIG. 23 so that the cutters 3 form a small cutout at the end of the support table 215. Then, the cutter assembly 11 is moved again downward along an inclined path that is still lower than and parallel to the first said path to make a second cut so as to make the cutout deeper. Such cutting is repeated until the desired cutout 215A is formed at the end of the support table 215, as shown in FIG. 25. Thus, the wood board 210 is supported from the bottom in contact with the support table 215 except the area of the bottom just above the cutout 215A of the support table 215.
In preparing a second wood board that is to be joined end-to-end to the above wood board 210 already formed with the bevel cuts 210A, the second wood board is stopped at the same position on the support table 215 as in the case of the wood board 210 and then shifted in the direction that is perpendicular to the board feeding direction for a distance corresponding to half of the width of the cutter 3. With the second wood board thus set on the support table 210, the cutters 3 rotating in arrow direction are moved past the end of the second wood board thereby to form a series of similar bevel cuts. In joining the first and the second wood boards together, either one of the boards is inverted or turned upside down and the bevel cut end surfaces of the two boards are coated with adhesive and fitted together.
In the above method, however, if any part of the end of the wood board 210 has an upward bend or warp 210B as indicated by chain double-dashed line in FIG. 23, such bent part of the end is cut deeper than the other part of the end 210B, with the result that a void is formed in the joint formed by two opposing ends of two wood boards and the desired joint strength fails be to be achieved. A wood board made by joining two such boards may be broken at the joint when subjected to application of any force.
The present invention, which has been made in light of the above-identified problems, is directed to providing a method for forming a bevel cut at an end of a wood member which can solve the above-identified problems.